In light of the ever-rising number of automobile collisions, a great deal of research has been conducted on ways to reduce the severity of injuries sustained by passengers in an automobile during an automobile collision. In particular, efforts have been directed toward developing headrests that reduce the severity of whiplash injuries. Examples of such devices are shown in Japanese Patent Application Publication No. 2006-182276 and Japanese Patent Application Publication No. 2007-55500, both of which disclose use of a sensor to detect the distance to an adjacent vehicle. Based upon the distance to an adjacent vehicle, a computer determines whether a collision is imminent, and, if so, tilts the headrest forward. Moving a headrest forward during an automobile collision is known to reduce the severity of whiplash injuries by reducing movement of the vehicle occupant's head in a backward direction. In particular, when a collision occurs, the vehicle occupant's head shifts forward, then immediately after, the vehicle occupant's head moves backward. When the vehicle occupant's head moves backward, a huge force is applied to the vehicle occupant's neck, which causes whiplash. Accordingly, known active headrest devices move the headrest forward to help reduce the extent of backward movement of the head during a collision to help mitigate the whiplash effect.
Also, there are known headrests that include means to adjust the height of the headrest. For example, the driver can get a better rear view if the headrests in the back seats of the vehicle are lowered. Passengers in the back seat can get a better front view if the headrest of the front passenger seat is lowered. Furthermore, the driver can get a better side view if the headrest of the front passenger seat is lowered. Also, in case if there are three rows of seat in a car, by lowering the headrest in the middle row, both front and rear view will be improved. However, the known headrest devices have complicated structures that are costly to produce. Also, these complicated structures can lead to various problems, such as frequent device failure, lowered reliability and increased maintenance costs. Furthermore, known headrests that can change their height still block the view because of the presence of the headrest itself on the car seat.
For the problem of whiplash injury, the most important solution is to move the headrest forward without fail whenever there arises a danger of collision. Therefore, a low cost reliable headrest device with such function is desired.
Accordingly, it would be desirable to have a headrest device that includes a simple, yet reliable structure operative to move the headrest in the event of a collision or in order to reduce the sight obstruction caused by the headrest.